Of course, you just need to make sure your power supply, however it is set up, needs to provide constant power over long term that the system needs at minimum. That means for ex. if you use solar, you need to have a big enough battery and array so that it can charge batteries throughout the day even when it’s cloudy so the system can be up overnight when there is no power generation happening. If you have for ex. a raspberry pi and a smartphone as a hotspot, you can probably have enough energy with an average UPS and one solar panel to make sure it will never go fully empty overnight, regardless how cloudy the day was.